Hydraulically powered AC generators are useful for a variety of applications. Such generators may be used, for example, to drive various components of large vehicles, such as fire trucks. Hydraulically powered AC generators are controlled by regulating an amount of hydraulic fluid used to drive the generators. If the amount of hydraulic fluid used to drive the generator is not controlled accurately, the power output of the generator will vary from a desired power output. This can result in reliability issues for the components powered by the generator.